Inflatable balloons and kite-like lighter-than-air-structures have been utilized in the past for search and rescue, and just for the enjoyment of flying them. Such structures can to be used to save lives when a boatsman, hunter, hiker or other outdoorsman becomes lost, injured or otherwise in need of help. Many times such individuals are not equipment with radio devices to accomplish the communication necessary to assist in locating them. While organized search and rescue teams are often able to locate an injured or lost person, the search is made difficult and sometimes impossible by rough terrain, weather, nightfall or the large expanse needed to be searched.
While simple balloons filled with helium rise vertically in situations where there is no wind, even a slight wind is often enough to cause them to blow downwind and lose significant altitude. As such, they are not as visible to a searcher and the tether line or even the balloon itself can become entangled in trees. High winds can blow the balloon completely to the ground. Presently known inflatable kites exhibit similar characteristics.
Another disadvantage of inflatable balloons and kites is that they lose considerable altitude when exposed to rain as a result of water droplets that accumulate on their surface. Furthermore, if released from under the water, such as is necessary when used as a signal device for location and recovery of sunken marine craft, they will many times not exit the water. The adhesive force the water applies to the device and the weight of any water that may collect on top of the device tends to keep the device trapped at the water's surface.
Particularly when used for the location and recovery of unmanned marine craft, it is important to have a signal device which automatically releases itself from its source of inflation upon reaching full inflation. Moreover, unlike some existing inflatable airfoil designs, no rigid stays should be required. This allows compact storage when deflated, and requires no manual operations to put the rigid stays in place in preparation for inflation.
In the past many airfoils have had a design which inherently require they have many control lines connecting them to the ground in order to fly. Having more than one such control or tether line increases the chance of entanglement and makes the stowage and release of the device more difficult and manufacture of the device more expensive. Furthermore, an airfoil with multiple control lines may require adjustment of the lines during flight to maintain altitude and a proper attitude. As such, the airfoil would be of little value for situations where the person using the airfoil was injured and unable to attend to flying the airfoil or where no person was available such as the recovery of an unmanned marine craft.
It will therefore be appreciated that there has been a significant need for an inflatable airfoil for use in search and rescue and for location of marine craft. When deployed, the airfoil should maintain its altitude even in severe winds and when exposed to rain. Furtermore, the airfoil should be able to exit the water without assistance if inflated while under the water. Particularly in this situation, the airfoil should provide means for self-activated release from its source of inflation. The airfoil should be of a non-rigid construction requiring no stays for stiffening, and be deployable merely by inflation without requiring the presence of a person to fix stays or otherwise prepare the airfoil for flight.
The airfoil should only require a single-point attachment to a single tie down line and require no user attention during flight. The airfoil should have a positive lift when exposed to wind sufficient to lift its own weight even without being inflated with a lighter-than-air gas so that it does not rely solely upon the gas to maintain its altitude. The airfoil should have a sufficiently small size so that it can be easily folded or stuffed into a small container, and be filled with a lighter-than-air gas such as helium from a reasonably small pressure bottle. When filled with lighter-than-air gas, the interior gas containing volume of the airfoil should be sufficient that the buoyancy of the gas will cause the airfoil to rise even in a condition of no wind. Moreover, the airfoil should have a simple and relatively inexpensive construction.
The present invention fulfills these needs and further provides other related advantages.